Tuning FX Impact Mk2/M3 - slower first shot - no reg creep - quasi-scientific analysis

[Superpete]

I think FX left white o-rins dep there and not contacting the black bushing so the black bushing not pressing on the white oring and not compressing it under its force, who knows what they were thinking, but I like the concept. In order to drill it correct depth we would really need some precise maching to kae that hole just so.

 

[GMANCO]

Instead of drilling that conical section out to create a flat seat area and "risking" violating min thickness, could you press fit a soft metal plug into that conical section and then drill a clean hole for the rod to pass through?

 

[Airgunnerscott]

Instead of drilling that conical section out to create a flat seat area and "risking" violating min thickness, could you press fit a soft metal plug into that conical section and then drill a clean hole for the rod to pass through?

mubhaur on this forum has the answer for this problem....I been using it for a couple months now and have no slow first shot at all anymore.... Even after a couple days off sitting.....
Someone just needs to take his design and have it mass produced and stop trying to fix an old defective part I think..

 

[Superpete]

Instead of drilling that conical section out to create a flat seat area and "risking" violating min thickness, could you press fit a soft metal plug into that conical section and then drill a clean hole for the rod to pass through?

That a good idea, a aluminum insert, thats it.

 

[GMANCO]

That a good idea, an aluminum insert, thats it.

Or that peek material you used could work also.

 

[GMANCO]

mubhaur on this forum has the answer for this problem....I been using it for a couple months now and have no slow first shot at all anymore.... Even after a couple days off sitting.....
Someone just needs to take his design and have it mass produced and stop trying to fix an old defective part

I’d be a buyer for sure!

 

[mubhaur]

mubhaur on this forum has the answer for this problem....I been using it for a couple months now and have no slow first shot at all anymore.... Even after a couple days off sitting.....
Someone just needs to take his design and have it mass produced and stop trying to fix an old defective part I think..

View attachment 589678

By the grace of God I didn't receive any negative feedback on this part yet.

I just wanted to help out airgunning community. The problem is this that there is very thin profit margin on this part. Such things cannot run the kitchen. I am a professional accountant and airgun modification is just my hobby. My machinist makes these parts on manual laith machine and it takes him more than two days to make one part.

I have shared the details of this part with Huma-Air for mass production without charging them money.

Huma clearly refused as perhaps this is also not a good profit making item for them.

Mubhaur

 

[Apollo]

I think FX left white o-rins dep there and not contacting the black bushing so the black bushing not pressing on the white oring and not compressing it under its force, who knows what they were thinking, but I like the concept. In order to drill it correct depth we would really need some precise maching to kae that hole just so.

Pressing the bushing against the o-ring is indeed never the intention, but I assume that if you press it, you want it to be at a fixed distance just behind the o-ring without the 2 mm clearance it currently has.
Unless the bushing really has no other purpose than to more or less hold the o-ring in place when it is not under pressure.

 

[Apollo]

Instead of drilling that conical section out to create a flat seat area and "risking" violating min thickness, could you press fit a soft metal plug into that conical section and then drill a clean hole for the rod to pass through?

I fear this would increase the risk of leaks.

There is room to drill the seat flat.
The question is, how far, and is the part that is modified by FX and currently installed on the M4 and sold as a spare within tolerance?
If so, it would be helpful if FX could confirm this.
This is a simple question asked out of genuine concern, not emotion or a desire to cause fuss.
Hopefully, this concern is unfounded, as I have an M4 on my shortlist and therefore, confirmation would be greatly appreciated.

 

[Apollo]

To show the difference in thickness, the old one is on the left, the new one on the right:

 

[Apollo]

Yesterday, I installed the new plenum end piece without the plastic bushing, but with the supporting o-ring (5.5x1.5 NBR70) so that the new o-ring (2.9x1.78 PUR90) stays in place during installation.

Today, I checked and saw that everything had remained under pressure whitout a leak, so I decided to test it.
The first shot was 3 fps slower than the last one yesterday.

Yesterday, after reassembling it, I didn't adjust it very precise and there was a 10 fps spread, so I can't even say if it still had an effect after 24 hours.

It now really seems that drilling the conical seat flat was the solution.
Why it took so long or why they had to drill it out so far is something I'll never know.

It's also clear that the bushing only serves to keep the o-ring more or less in place during assembly.
Anyway, fortunately, it works just as well without the bushing and with the supporting o-ring.

 

[DesertSilver]

It also gives you just a little bit more plenum capacity.

 

[Apollo]

0,05 cc to be exact

 

[DesertSilver]

It looked like more than that.

 

[av8torgc]

The M3 and first M4 had the same part.
FX is currently modifying this part, and the new or modified part is now being installed on the M4.

It can also be ordered as a spare part. It has the same part number: 10338

Today I had an interesting conversation with Utah Airguns. The person I spoke with (who said they verified this with one of their airgun techs), said they were not aware of any slower first few shot issues with the M3. They said they are only aware of issues with the M4, and stated the solution was to go back to the M3 type o-rings to solve the problem which is definitely not the solution.

I had contacted them to see if I could purchase one of the new power plenum valvetube ends (P/N 10338) that Apollo has shown had been recently released. Utah Airguns was not aware of any change, and said the ones they had in stock were still the same original M3 design.

Apollo: For clarification are you installing the new design power plenum on an M3 Impact (sorry if you already stated that somewhere earlier)? And where were you able to obtain this new part, or do you have a newer M4 that had this new design part already? I see you are located in Belgium, so it appears this info and part hasn't made it to the USA yet.

 

[Apollo]

If it wasn't a problem, they solved it anyway with their modified part

At least at the 100 bar at which I tested it.
It is possible that at a higher plenum pressure of up to 160 bar, more pressure will be put on the o-ring, causing it to stick again but most likley not.

Recent M4s were equipped with this modified part, so I assume that most recent M4s have the modified plenum end piece, as well as the updated valve stem.
The first M4s did not have these new parts.

The modified part is now also supplied as a spare part. If it is not yet available in the US, I assume it will follow soon.

Hopefully, they will continue to supply it without pressing the bushing into it, as this can also be done with the supporting o-ring, making it easier if the o-ring ever needs to be replaced.